Time-limit device



Aug. 13, 1929. L. s. WALLE ET AL 1,724,863

TIME LIMIT DEVICE Filed Jan. 25, 1926 h'wvencor 6 Harold \A/. Brown,

Ludv g' S. Wane, y M f Their Ak'bor ey.

Patented Aug. 13, 1929.

UNITED STATES PATENT OFFICE.

LUIJVIG S. WALLE, OF SCOTIA, AND HAROLD W. BROWN, OF SCHENECTADY, NEWYORK, ASSIGNORS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TIME-LIMIT DEVICE.

Application filed January 23, 1926. Serial No. 83,411.

Our invention relates to improvements in time limit devices and moreparticularly to improvements in time limit electroresponsive devices,such as relays, for use in the protection of electric systems. An objectof our invention is to provide an improved time limit electroresponsivedevice which is normally inactive but is definitely acuated only when anelectric quantity such as the current of a circuit exceeds apredetermined value and which, without the expenditure of a relativelyexcessive amount of power, has almost instantly available at theexpiration of a time dependent on the value of the electric quantity aforce amply sufiicient to actuate a movable member for example one of apair of relatively movable cooperating contacts.

Our invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims. a

The single figure of the accompanying drawing illustrates a time limitelectroresponsive device embodying our invention. This device, inaccordance with our invention, comprises a movable member 1 and meanscomprising an energizing winding 2 constructed and arranged to restrainthe member 1 against movement when the current in the winding 2 is lessthan a predetermined value and to move the member when the currentexceeds such value. For utilizing the movement of the member 1, when itattains a predetermined or critical speed, means such as a centrifugalmechanism 3 is provided. This speed responsive mechanism may be arrangedto control an actuating means comprising one or more movable members 4which may actuate one of a pair of relativel movable cooperatingcontacts 5, 6 arrange to control a circuit 7 such as, for example, thecircuit of the controlling coil of a circuit breaker.

The movable member 1 and the controlling means therefor may be and isshown of the induction disc motor type, the member 1 being the discwhich is secured to a suitably journaled shaft 8. The controlling means,

or motor element which is inductively related to the disc, iselectromagnetic and as illustrated comprises a plural branched core 9and a cooperating magnetic member 10 between the poles of which the disc1 is mounted. The core 9 provides two magnetic circuits which comprisethe core branches 11 and 12 and which have the common energizing winding2. The core branches 11 and 12 are provided with shading or shortcircuited windings 13 and 14 respectively, which cooperate with thewinding 2 to exert torques on the disc 1 in a well known manner. Inorder to have the centrifugal mechanism 3 normally inactive, theseshading windings are so arranged that the torques are opposed and withcurrent in the winding 2 less than a predetermined value, their resultant effect is approximately zero, that is,

when the excitation of the driving magnet 910 is below a predeterminedamount. In order, however, to have the centrifugal mechanism 3positively actuated when the current in the winding 2 exceeds thispredetermined value, that is to have a definite pickup point, the motoris arranged to provide a torque suflicient to accelerate the disc 1 androtate it at a speed dependent on the current. For this purpose, one ofthe magnetic circuits, such as that comprising the core branch 12, maybe arranged to saturate at the predetermined current as by providing thebranch 12 with a portion 15 of restricted cross-section. Then when thecurrent that is to say the excitation of the driving magnet 910 exceedsthe predetermined value, the torque exerted by windings 2 and 14 isexceeded by the torque exerted by windings 2 and 13, and the greater thecurrent the greater the difference between the torques.

The building up of the speed of the disc 1 will be retarded by theinertia of the rotating parts including the disc and the centrifugalmechanism 3. This mechanism may comprise, as shown, two weights or balls16 pivotally mounted on a member, such as the shaft 8, which is rotatedby the disc 1. At the expiration of a time dependent on the current inthe winding 2 and the inertia of the rotating parts, the disc 1 willattain a 1 critical speed suiiicient to cause the weights 16 to fly outand raise a member such as a flanged collar or weight 17 which isslidably mounted on the shaft 8 and which may be biased to the positionshown by a spring 18, as well as gravity. This collar- 17, when movedthrough a suitable distance, engages the controlling member A and in thearrangement shown opens the contacts 5 and 6.

1W ith this arrangement, the downward force comprising the weight of thecollar 17, the bias of the spring 18, and the weight of the balls 16,tends to maintain the balls in the position shown. lVhen the disc 1attains a speed such that the centrifugal force acting on the balls 16is suiiicient to overcome this downward force, the balls fly out veryquickly with considerable force. While the torque due to the weight ofthe balls 16 tends to increase as they move farther from the shaft, thisincrease is offset by the decrease in the torque exerted by the weightof the collar 17 and the bias of the spring 18 as the arms 19 of theball-supporting levers move toward the shaft.

For varying the time action of the device, the balls may be arranged tofly out at dif ferent critical or predetermined speeds of the disc 1 ina number of ways, for example, by"

having the spring 18 adjustable so that. its force may be varied as by anut 20 on the shaf 8-. V

r The force available to operate the contact mechanism, being derivedfrom the accelera- 35 mined speed. Consequently, the relay is "soparticularly applicable where it is desired to have circuit 0 eningaction in circuit breaker control circuits on the occurrence of abnormalcircuit conditions. By reason of the large available force,othersuitable contact arrangements such as the well known toggle hand-resettype may, of course, be used. Vhen the winding 2 is deenergized as bythe opening of the line circuit breaker, the disc 1 ceases to rotate andthe weights 16 and the collar 17' resume the position shown in thedrawing, the contacts 5 and 6' reclosing, if

desired, by having the weight distribution or the member 1' such as totend to turn it counterclockwise or using suitable resilient means. V

While we have illustrated and described a "particular embodiment of ourinvention and more particularly described its application to a systemwherein a single exc ting coil is responsive to the current. in aclrcuit so as to produce operation when a predetermined connected torespond to various circuit conditions according to the particularapplication that it is desired to make of our invention. We, therefore,aim in the appended claims to cover all such changes and modific'ationsas fall within the scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States,

1. A time limit electroresponsive device comprising a movable member,means com prising an energizing winding for exerting opp'osing'forces onthe member constructed and arranged to exert forces whose resultantefiect is approximately zero. when the winding is energized by currentless than a predetermined value whereby to prevent movement of themember and to move the member when the current exceeds said value, acentrifugal mechanism arranged to be actuated upon movement of saidmember, and actuating means arranged to be controlled by the centrifugalmechanism when the member has acquired a predetermined speed.

2. A time limit electroresponsive device comprising a rotatably mountedmember, means comprising an energizing winding for exertlng opposingtorques on the member constructed and arranged to preventmovement of themember when the winding is energized by current lessthan a'predetermined value and to move the member when the current exceeds said value,and a normally inactive centrifugal mechanism associated with the memberand arranged to be actuated thereby.

3. A time limit electroresponsive device comprising an induction disc,electromagnetic means tending to rotate the disc in opposite directionscomprising an energizing winding and two windings cooperating therewith,said means being constructed and arranged to hold the disc againstmovement when the current in'the energizing winding is less than apredetermined value and to move the disc when the current exceeds suchvalue, and a normally inactive centrifugal mechanism arranged to beactuated by the 'disc when the disc attains a predetermined speed. 7 I

1. A time limit electroresponsive device comprising an induction disc,means tending to rotate the disc in opposite directions for normallyholding the disc against movement comprising an electromagnet havingtwo-flux circuits, an energizing winding for the flux circuits, one ofsaid circuits being arranged to saturate with current in 'excessof apredetermined value in said winding whereby to effect rotation of thedisc in one ofs'aid directions at a speed dependent on the value of thecurrent in the winding, a normally inactive centrifugal mechanismarranged to be actuated upon a predetermined speed of rotation of thedisc and relatively movable cooperating contacts arranged to becontrolled by the mechanism.

5. A time limit electroresponsive device comprising an induction disc, amotor element for rotating the disc inductively related thereto andarranged to exert opposing torques thereon, and speed responsive meansoperative on the occurrence of an unbalance between said torquessufficient to move said disc at a predetermined speed.

6. A time limit electroresponsive device comprising a movable member,and electromagnetic means for rotating the member arranged withexcitation below a predetermined amount to exert approximately equalopposing torques on the member and with excitation above said amount tobring the member up to a predetermined speed in a time dependent on theinertia of the memher and the amount of excitation, and circuitcontrolling means responsive to the speed of said member.

7 A time limit electroresponsive device comprising a movable member anda motor element for moving the member arranged to exert opposing torquesthereon, and a normally inactive centrifugal mechanism operative on theoccurrence of an unbalance between said torques sufiicient to move saidmember at a predetermined speed.

8. A time limit electroresponsive device comprising a rotatable member,a motor element for rotating the member arranged to exert opposingtorques thereon, circuit controlling means and a centrifugal mechanismfor actuating the circuit controlling means on the occurrence of anunbalance between said torques suflicient to move the rotatable memberat a predetermined speed.

9. In combination, a member to be operated, a motor of the inductiondisc type having electromagnetic means for producing opposing torques onthe disc arranged to balance each other when the energization of theelctromagnetic means is below a predetermined amount characterized bythe fact that a portion of the electromagnetic means is arranged tobecome saturated on energization thereof above said amount whereby tounbalance the torques and move the disc, and means controlled by thedisc for actuating the member to be operated.

In witness whereof, we have hereunto set our hands this 22nd day ofJanuary, 1926.

LUDVIG S. lVALLE. HAROLD lV. BROWN.

